1. Field of the Invention
The present invention relates generally to signaling devices and more particularly to an improved light emitting diode signaling device and a method of providing an indication using the same.
2. Background Information
Light emitting diodes (LEDs) are replacing incandescent bulbs in various types of signaling devices such as, for example and without limitation, traffic signals, railroad crossing signals, and railroad wayside signals. An LED signaling device (i.e., a signaling device incorporating LEDs as an indication source) consumes less power, provides increased reliability, and requires less maintenance than a comparable incandescent signaling device (i.e., a signaling device incorporating an incandescent bulb as an indication source).
Older generation LEDs used in LED signaling devices, however, have several limitations. For example, the luminous output intensity of individual older generation LEDs is fairly low. As a result, dozens and sometimes hundreds of LEDs must be employed to generate the minimum luminous output intensity for certain signaling devices. The use of large numbers of LEDs, however, increases the manufacturing, operating, and maintenance costs of the LED signaling device. Additionally, the amount of space needed to accommodate the large number of LEDs make retrofitting some existing incandescent signaling devices prohibitive.
LED technology has continued to improve. For instance, newer generation LEDs are capable of generating a higher luminous output with lower power consumption than older generation LEDs. Thus when employed in a signaling device, fewer new generation LEDs are needed to meet the minimum luminous output intensity requirements for the signaling device. The use of fewer LEDs, however, may cause uniformity problems. Specifically, the use of fewer LEDs may undesirably increase the potential for viewing one or more of the LEDs as an individual point source and/or may undesirably increase the potential of creating shadows. A typical uniformity requirement may demand that the ratio between the greatest luminance LED and least luminance LED in the signaling device must not exceed 5:1 when measured over average areas of 500 mm.
Thus, a need exists for an improved LED signaling device which employs fewer LEDs, which meets or exceeds minimum luminous output intensity requirements, and which meets or exceeds minimum uniformity requirements. A method of providing an indication using the improved LED signaling device is also needed.